Despite lingering questions, the Transportation Security Administration plans to start testing a new passenger identification system within the next couple of months.

Despite lingering questions, the Transportation Security Administration plans to start testing a new passenger identification system within the next couple of months. If all goes well, the system could be in place nationwide by the end of the year or early next year.

But significant hurdles remain. Privacy advocates say the system is too invasive and could potentially threaten civil liberties. Some members of Congress have hinted they may try to hold up funding for the effort.

The highly controversial Computer Assisted Passenger Prescreening System, commonly referred to as CAPPS II, is designed to flag suspected terrorists or other dangerous passengers before they board a plane. CAPPS II, announced in January, is intended to replace an existing program that airlines created in 1996.

After receiving more than 200 comments about its initial CAPPS II proposal, TSA released an interim final rule on the program Thursday. The revised proposal makes significant modifications to the original, including limiting the amount of time the agency will keep files on passengers. Originally, TSA planned to keep such information for 50 years. Under the interim rule, the data will only be held for a few days after a flight.

Additionally, TSA appears to have backed off a proposal to tap into a broad array of databases-including commercial sources, such as banks and credit reporting services-for information about travelers. The new rule says the agency will limit its data collection to the passenger's name, address, telephone number and date of birth. TSA says it will not ask commercial data providers for anything other than an "authentication score and code indicating a confidence level in that passenger's identity."

Still, under the rule, TSA will not divulge exactly where the information it gathers on passengers comes from. That raises red flags for privacy advocates such as David Sobel, general counsel at the Electronic Privacy Information Center in Washington.

"We think this system should be as transparent as possible," he said. "Public oversight and accountability is very important. This program can't be shrouded."

Sobel also raised concerns that the rule allows TSA to extend its reach into general police work. Under the rule, TSA will notify law enforcement authorities of any passenger with an "outstanding state or federal arrest warrant for a crime of violence."

TSA officials did not respond to calls for comment.

Reflecting the growing tension in the agency between its security mission and maintaining customer service for travelers, TSA Administrator James Loy said in a statement that CAPPS II will not only help identify potentially dangerous passengers, but also "be a valuable tool in holding down passenger wait times by reducing the number of people who undergo secondary screening or who are misidentified as potential terrorists." Lockheed Martin won the $12.8 million contract to build CAPPS II earlier this year.